Authorities pour more resources into their efforts as they comb a home linked to Steve Aisenberg.

LAND O'LAKES -- The search for the remains of Sabrina Aisenberg intensified Thursday at a home in the Pasco County subdivision where her father, real estate agent Steven Aisenberg, used to work.

With sniffing dogs, drilling equipment, saws and ground-penetrating sensor, a caravan of investigators showed up at 9 a.m. to continue their search for the infant, who disappeared in November 1997 from her Valrico home, 35 miles southeast of the neighborhood.

At the time the 5-month-old disappeared, Steven Aisenberg was employed by M/I Schottenstein in an office across the street from a construction site that now isthe home investigators have been scouring since Monday.

He also sold many of the homes in the subdivision, including the one being searched.

Investigators Thursday led one German shepherd around the perimeter of the house and took another through the front door.

From a vacant sandy lot about 50 yards behind the house, investigators could be seen moving patio furniture and sweeping the screened pool area with sensor.

In the seven hours they occupied the house, investigators ignored the media personnel swarming around the residence, refusing to say whether any evidence had been found.

But the silence spurred rumors and frustration among neighbors, many of whom gathered on the sidewalks to gawk at the forest of TV news antennas and the army of photojournalists shooting the slightest movement.

The house that investigators are searching began as a model for M/I Homes.

The building permit shows that the inspection of the concrete foundation took place the same day it was poured, on Dec. 29, 1997, almost exactly a month after Sabrina disappeared.

The house was unoccupied until the current owners bought it on May 20, 1999, according to Pasco County court documents.

Court records show that detectives previously tested the concrete slabs of at least eight other homes built by Aisenberg's former employer, but it is unclear where because addresses were not disclosed.

Neighbors who have lived in the development since before Sabrina's disappearance said no investigators had visited their neighborhood until this week.

"What I wonder is, why didn't they come out here for three years?" said neighbor Chuck Boltze. "I never saw anybody out here. Nobody did. They didn't even drag the ponds. I hope they're not just grabbing for straws."

Marsha McCreary, vice president of the Willow Bend Homeowner's Association, said authorities called the organization several weeks ago to say they might dive-search a pond about 150 yards behind the home.

McCreary said she wasn't sure which county's sheriff's office called, or whether the pond ever was searched. She also didn't know whether the call was related to the search for Sabrina.

"We told them there was no problem (with diving the pond)," McCreary said. "I'm not saying it was associated with this. But it is does seem kind of strange."

The rekindled search for Sabrina comes at a time when a federal case against Steve and Marlene Aisenberg appears on the verge of unraveling.

The two parents, who have denied any involvement in their daughter's disappearance, were indicted last September by a federal grand jury in Tampa on charges of conspiracy and making false statements about the incident.

Investigators bugged their home in the days after Sabrina was reported missing and claim to have recorded the couple talking about the child's death.

But the tapes have come under serious attack, with one audio expert hired by the defense saying he can't make out any incriminating statements.

On Monday, the same day investigators began searching the Pasco home, U.S. Magistrate Judge Mark Pizzo ordered an evidentiary hearing to determine whether Hillsborough detectives lied or misrepresented facts to a circuit court judge in their application to wiretap extensions in early 1998.

On Wednesday, U.S. District Judge Steven McKay agreed to postpone the hearing, originally scheduled to begin Monday, for 30 days.

The Aisenbergs moved to Maryland last spring.

Steven Aisenberg told a reporter at his Maryland home Wednesday that the couple thinks Sabrina still is alive and that he is outraged at the search. Law enforcement officials have said they think Sabrina is dead.

Aisenberg attorney Barry Cohen declined to comment Thursday.

- Times reporters Ryan Davis, Collins Conner and Chris Goffard and Times researchers Kitty Bennett and Caryn Baird contributed to this report.